Diaphragmatic contribution to gastroesophageal competence and reflux in dogs

Martin, C. J.; Dodds, Wylie J.; Liem, H. H.; Dantas, Roberto Oliveira; Layman, Rick D.

doi:10.1152/ajpgi.1992.263.4.g551

Cited by 34 publications

(45 citation statements)

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“…The LES (24,25,31), as well as the DH (19,21), provides the barrier between the proximal stomach and esophagus that prevents GER, and we found, as others have reported (22)(23)(24)28), that both are inhibited during the first phase of eructation. Not only are the LES and DH inhibited, but there is a very close temporal relationship between these inhibitions, suggesting a functional and mechanistic relationship.…”

Section: Discussionsupporting

confidence: 88%

Digestive and respiratory tract motor responses associated with eructation

Lang

Medda

Shaker

2013

American Journal of Physiology-Gastrointestinal and Liver Physi

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Lang IM, Medda BK, Shaker R. Digestive and respiratory tract motor responses associated with eructation. Am J Physiol Gastrointest Liver Physiol 304: G1044 -G1053, 2013. First published April 11, 2013 doi:10.1152/ajpgi.00043.2013.-We studied the digestive and respiratory tract motor responses in 10 chronically instrumented dogs during eructation activated after feeding. Muscles were recorded from the cervical area, thorax, and abdomen. The striated muscles were recorded using EMG and the smooth muscles using strain gauges. We found eructation in three distinct functional phases that were composed of different sets of motor responses: gas escape, barrier elimination, and gas transport. The gas escape phase, activated by gastric distension, consists of relaxation of the lower esophageal sphincter and diaphragmatic hiatus and contraction of the longitudinal muscle of the thoracic esophagus and rectus abdominis. All these motor events promote gas escape from the stomach. The barrier elimination phase, probably activated by rapid gas distension of the thoracic esophagus, consists of relaxation of the pharyngeal constrictors and excitation of dorsal and ventral upper esophageal sphincter distracting muscles, as well as rapid contraction of the diaphragmatic dome fibers. These motor events allow esophagopharyngeal air movement by promoting retrograde airflow and opening of the upper esophageal sphincter. The transport phase, possibly activated secondary to diaphragmatic contraction, consists of a retrograde contraction of the striated muscle esophagus that transports the air from the thoracic esophagus to the pharynx. We hypothesize that the esophageal reverse peristalsis is mediated by elementary reflexes, rather than a coordinated peristaltic response like secondary peristalsis. The phases of eructation can be activated independently of one another or in a different manner to participate in physiological events other than eructation that cause gastroesophageal or esophagogastric reflux.belching; gastrointestinal motor activity; pharynx; larynx; esophagus SOME OF THE MOTOR EVENTS associated with eructation are known, i.e., upper and lower esophageal sphincter (UES and LES) relaxation (13,15,16,(23)(24)(25)31), glottal closure (26), changes in respiration (11,22), and retrograde esophageal peristalsis (11), but the specific muscles that accomplish these functions are unknown or incompletely known. Other functions during eructation, e.g., opening of the UES, have not been investigated. Moreover, while some of the motor responses during eructation have been identified, as noted above, most studies focused on only one muscle or function, and the relationship among functions and motor responses producing the effects of eructation has not been investigated. Therefore, while it has been determined that transient LES relaxation (TLESR), as well as relaxation of the UES, is associated with eructation (23), the relationship between TLESR and UES relaxation during eructation is unknown.

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Section: Discussionsupporting

confidence: 88%

Digestive and respiratory tract motor responses associated with eructation

Lang

Medda

Shaker

2013

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…Enhanced contraction of the crural diaphragm may have contributed to the hypoxia-induced increase in LES tone (27). There is ample evidence in animal and human studies that contraction of the crural diaphragm increases pressure at the esophagogastric junction (27,28). However, in our study, this increase in LES pressure was abolished by muscarinic blockade without affecting the diaphragmatic response, suggesting a central origin for this association.…”

Section: Discussioncontrasting

confidence: 65%

Effects of Hypoxia on Respiratory Neural Output and Lower Esophageal Sphincter Pressure in Piglets

et al. 2002

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We have previously documented anatomic and functional relationships between ventilatory and autonomic neural output. Therefore, we hypothesized in this study that hypoxia-induced changes in respiratory neural output are associated with changes in autonomic regulation of lower esophageal sphincter (LES) pressure. Respiratory neural output, heart rate, and LES pressure were measured before and during a 3-min exposure to 8% oxygen (balance nitrogen) in 12 3-to 7-d-old piglets. Respiratory neural output was determined from diaphragmatic electromyogram and LES pressure from an esophageal catheter. Studies were repeated after atropine administration in eight animals. Hypoxic exposure resulted in significant increases in diaphragmatic amplitude, respiratory rate, and minute diaphragmatic activity as well as heart rate. The biphasic response of diaphragm amplitude peaked at 1 min, whereas the responses of respiratory frequency and heart rate were sustained. Hypoxia caused a 50% increase in LES pressure (p Ͻ 0.05), which was eliminated by i.v. atropine administration. Development of apnea during subsequent hyperoxic exposure was always followed by a decline in LES pressure. Hypoxia-induced increase in respiratory neural output and accompanying increase in heart rate are associated with enhanced constrictive output to the LES. Blockade by atropine implicates a peripheral cholinergic mechanism for this LES response. We speculate that whereas hypoxia in the presence of enhanced respiratory neural output seems to be protective against reflux, decreased respiratory drive and accompanying apnea may be associated with a decline in LES tone and predispose to gastroesophageal reflux. Neuroanatomic studies have identified that neuronal circuits involved in coordination of respiratory control are linked to parasympathetic motor output from vagal preganglionic neurons in the brainstem (1, 2). A functional role for such interconnections has been documented in several species, including puppies and piglets (3, 4). For example, hypoxic stimulation in piglets is associated with an increase in both phrenic neural output and contractile responses in peripheral airways and/or lung parenchyma, which are cholinergically mediated (5). This is consistent with the clinical observation that an acute reduction in inspired oxygen may lead to airway constriction in infants with chronic lung disease (6).Vagal preganglionic neurons, including neurons of the DMV, also contribute preganglionic parasympathetic motor innervation to the LES (7). Therefore, alterations in respiratory neural output elicited by chemoreceptor stimulation might be expected to modulate LES pressure. This would be of particular interest during early maturation, as recurrent apnea with resultant desaturation and gastroesophageal reflux are both common in premature infants, although their relationship is controversial (8 -11) and difficult to simulate in an animal model. In the current study, we therefore used a piglet model to test the hypothesis that hypoxia-induced changes in r...

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“…It is now clear, however, that along with the LES, several other regions i.e., the esophagus (27), stomach, and crural diaphragm, are inhibited during TLESR. Crural diaphragm inhibition during TLESR has been reported in humans (21) and dogs (17,24). It seems that the inhibition of the crural diaphragm is essential for the occurrence of gastroesophageal reflux during TLESR, because in the absence of LES tone, gastroesophageal reflux does not occur unless there is inhibition of the crural diaphragm (12,20,22).…”

Section: Discussionmentioning

confidence: 97%

“…During TLESR, along with LES, there is also inhibition of the other major component of the antireflux barrier, i.e., the crural diaphragm (21). Distension of the stomach in dogs induces TLESR, which is also associated with inhibition of the crural diaphragm (17). Simultaneous relaxation of the LES and inhibition of crural diaphragm also occurs during distension of the esophagus in cats (1).…”

mentioning

confidence: 98%

Baclofen blocks LES relaxation and crural diaphragm inhibition by esophageal and gastric distension in cats

Liu

Pehlivanov

Mittal

2002

American Journal of Physiology-Gastrointestinal and Liver Physi

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Recent studies indicate that baclofen decreases the frequency of TLESR; however, its effect on the crural diaphragm is not known. We evaluated the effects of baclofen on LES relaxation and crural diaphragm inhibition induced by gastric distension and esophageal distension in cats. Five adult cats underwent surgical implantation of wire electrodes into the crural and costal diaphragm for measurement of their EMG activity, respectively. One week after the surgery, animals were lightly sedated and recordings were performed using a manometry catheter equipped with a 2.5-cm balloon. The effects of baclofen (10 mol/kg iv) on the graded esophageal distension and gastric distension-induced LES and crural diaphragm responses were studied. Distension of the esophagus and stomach induces relaxation of the LES and inhibition of the crural diaphragm, simultaneously. Baclofen blocks both the esophageal and the gastric distension-induced relaxation of the LES and inhibition of the crural diaphragm. The magnitude of response to baclofen was significantly larger for the crural diaphragm inhibition than for the LES relaxation. Baclofen, a GABAB receptor agonist, blocks the reflex inhibitory pathway to the LES and crural diaphragm. The reflex inhibitory pathway to the crural diaphragm is more sensitive to blockade by baclofen than the reflex LES inhibitory pathway. transient lower esophageal sphincter relaxation; gastroesophageal reflux; crural diaphragm; GABAB agonist TRANSIENT LOWER ESOPHAGEAL sphincter (LES) relaxation (TLESR) is the major mechanism of gastroesophageal reflux in normal subjects and patients with reflux disease (8, 23). Recent studies in animals and humans reveal that baclofen, a GABA B agonist, inhibits TLESR (3,11,13,28). Studies (10) documenting the blockade of TLESR by baclofen used the LES relaxation criteria to identify TLESR. During TLESR, along with LES, there is also inhibition of the other major component of the antireflux barrier, i.e., the crural diaphragm (21). Distension of the stomach in dogs induces TLESR, which is also associated with inhibition of the crural diaphragm (17). Simultaneous relaxation of the LES and inhibition of crural diaphragm also occurs during distension of the esophagus in cats (1). The effect of baclofen on the crural diaphragm inhibition during TLESR and esophageal distension is not known. The goals of our study were twofold: 1) to determine the effects of baclofen on the gastric distension-mediated LES relaxation and crural diaphragm inhibition, the two important components of the TLESR, and 2) to determine the effects of baclofen on the esophageal distension-mediated relaxation of the LES and inhibition of the crural diaphragm. MATERIALS AND METHODS Diaphragm electrodes implantation.These studies were conducted in five female adult cats, weighing between 3 and 3.7 kg. The protocol for the study was approved by The Animal Ethics Committee of the University of California, San Diego, and San Diego Veterans Affairs Hospital. Under general anesthesia induced by xylazine (1.5 m...

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Diaphragmatic contribution to gastroesophageal competence and reflux in dogs

Cited by 34 publications

References 0 publications

Digestive and respiratory tract motor responses associated with eructation

Digestive and respiratory tract motor responses associated with eructation

Effects of Hypoxia on Respiratory Neural Output and Lower Esophageal Sphincter Pressure in Piglets

Baclofen blocks LES relaxation and crural diaphragm inhibition by esophageal and gastric distension in cats

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